Lazy tong jack



Aug. 14, 1956 s. J. PlcKARD ETAL LAZY TONG JACK Filed May 3l, 1950 '3 Sheets-Sheet 1 .ffl/ft O INVENTORS SYDNEYA J; PICKARD Cmd A BRIAN A. SAWYER i, Ww ma 174'! v Aug- 14 1955 s. J. PlcKARD P -rAL 2,758,816

LAZY ToNG JACK F/ G 4 IINVENTORS SYDNEY J. PlcKARQ and BRIAN A.vsAwYER /l T'fornew Aug. 14, 1956 s. J. PlcKARD ETAL LAZY "roNG JACK 3 Sheets-Sheet 3 Filed May 51, 1950 .snnll M @Tm INVENTORS lz: SYDNEY J. PICKARD 0nd BRIAN A. SAWYER United States Patent LAZY ToNG JACK Sydney J. Pickard and Brian A. Sawyer, London, England, assignors to Smiths .lacking Systems` Limited, London, England, a British company Application May 31, 1950, Serial No. 165,218

5 Claims. (Cl. 25'4--126) This invention relates to lint-ing devices of the lazyetong or toggle link type, and especially to jacks for jacking up motor vehicles.

lt is Van object of the invention to enable a firm bearing Ito be achieved both on the ground and on the vehicle or other load irrespective of the camber or other inclination of the ground and of the angle of tilt of the vehicle during "lifting and at the same time to enable the jack Vto be conrVeniently' reached for opera-ting it. Y

According to one vfeature of the invention a lifting device of the type referred to has the upper ends of its opper links connected pivotally on a common axis on which also a load-engaging member is pivotally mounted, and the lower ends of the lower links connected pivotally on a common axis on which also a ground-engaging member is pivotally mounted, operating means being provided for moving the other ends of the links towards and away from each other. The load and ground-engaging members can thus tilt pivotally in relation to the remainder of the ja'ck to accommodate themselves to different angular dispositions of the load and ground. l

The load-engaging member may lbe constructed for attachment to the vehicle chassis or to any other part of the vehicle so that the jack is suspended from the vehicle and in operation is extended downwardly to engage the ground. The operating means may comprise a rotat-alble screw having one end journalled on a pivot block to which one pair of upper and lower links are pivoted, said screw engaging a nut which is non-rotatably att-ached to a second pivot block to which the second pair of upper :and lower links are pivoted. Conveniently lbo'th the upper links and both the lower links are of equal length and once the device has been extended with said groundengaging member in contact with the ground the load axis, i.v e. the plane through the pivoted upper ends of the upper links and the pivolted lower ends of the lower links, and the screw axis both become substantially xed. If, therefore, the screw is maintained substantially horizontal during the operation of extending the jack to engage the ground the load-axis will be substantially vertical. This, however, generally necessitates stooping on the part of the operator and there may often be a tendency to lift the louter end of the screw during the preliminary iititing operation with the result that the load axis becomes inclined, while in -addition the screw m-ay contact and damage the lower part of the body. If, under such conditions, the device should be used at the side of a vehicle on a sharply canilbered ground surface, the tendency may exist for the vehicle, once the load has been taken olf the Wheels at one side, to slew sideways and possibly slide olf or tip over the jack.

According to a further fea-ture of .the invention, this possibility may be avoided by the provision of resilient means interconnecting the load-engaging member andthe toggle system and tending to maintain said member 4in a predetermined mean angular position with respect to the toggle sys-tem. With the addition of such interconnecting means the angular position of attachment of the load- 'ice engaging member to the vehicle chassis will determine the angular position ofthe load axis in relation tothe chassis. The latter, for example, may be provided with a projection in the form of a rail along which the load-engaging member, which may be .of channel or claw shape, is slidable to a pre-determined position and the rail may be inclined to the chassis to an extent corresponding to the inclination of the load-engaging member relatively to the screw axis, thereby ensuring that the load axis is loc-ated in the required plane. In the operative position of the jack the load-engaging member preferably locates against an abutment on the rail which prevents further relative movement.

The aforesaid addi-tional connection between the loadengaging member and the toggle system may be effected by a link which extends parallel to one of the toggle links and is constructed in such manner that its length is resiliently variable upon the `applicati-on of a force thereto in either longitudinal direction. The resilience may be provided by means of a spring which is normally in a stressed condition so that it presents immediate resistance to deformation. The parallel link may have one end pivotally connected to the load-engaging member at a point olset from the point of pivot-al connection lof said member to the upper ends of the upper toggle links and its other end pivotally connected to a bracket which is lixed in relation to one of the piv-ct blocks connecting a pair of upper and lower links. Preferably the resilient link is located within the compass of the toggle link system so as not to increase the overall size of the device in the collapsed condition of the latter.

The resilient or parallel link may be constructed in the form of .two members which are assembled for relative longitudinal movement, a compression spring being iitted between said members so as to maintain the link at a pre-determined length (in relation to the parallel toggle link) while at the same time allowing for variation in said length in either direction with further compression of the spring so as to enable the load-engaging member to follow the inclination of the vehicle chassis by turning about its pivotal axis.

Instead of employing a parallel link as Iabove described, a laminated semi-elliptic leaf spring may be attached at its cen-tre to the lower side of the load-engaging member, the opposite downwardly curved ends of said spring engaging pins or like abutments on the two upper toggle links. The load-engaging member may carry two stops engaged by the under side of the spring on either side of the position of -attachment of the latter t0 said loadeng-aging member. These stops enable the spring loading to be relieved from one of said abu'tments when the spring loading is increased on the other side due to tilting of the load-engaging member in relation to the remainder of the jack. The abutments may be in a horizontal plane or one higher than the other, according to whether the noun-a1 position of the load-engaging member is required to be horizontal or tilted.

In order that the invention may be clearly understood and readily carried into effect, the same will now be more fully described with reference to the accompanying drawings, in which:

Figure l is a longitudinal sectional View of one form of motor vehicle lifting jack shown attached to a vehicle chassis;

Figure 2 is an end elevation of the jack shown in Figure l as seen from the left of said figure;

Figure 3 is a view similar to Figure l of another form of motor vehicle lifting jack according to the invention; yand Figure 4 is an end elevation of Figure 3 as seen from the left. of said figure.

Referring firstly to Figures l and 2, the device here illustrated comprises two similar laterally spaced toggle link systems, each system having a pair of upper links 10, 11 and a pair of lower links 12, 13, the corresponding upper and lower links of the two pairs being respectively interconnected by transverse plates a 11a and 12a, 13a welded thereto. At their upper ends the two pairs of upper links are pivoted on a transverse rod 14, the lower ends of the two pairs of lower links being similarly pivoted on a transverse rod 15. The other ends of the links of each system are connected together in pairs to provide a parallelogrammic assembly, each such pair, comprising one upper link 10 or 12 and one lower link 11 or 13, being pivotally carried on a pin 16 or 17 projecting laterally from a pivot block 18 or 19. The block 18 is secured by 'bolts 20 to a bracket 21 which surrounds a non-rotatable internally threaded sleeve or nut 22, said nut co-operating with a rotatable screw rod 23. One end of said rod has secured thereto a socket 24 for the reception of an operating handle or crank, and the other end has a reduced diameter portion 25 which is freely rotatable within the pivo-t block 17. A thrust ball race 26 is provided at this end of the screw and is held on the screw by a nut 27, the pivot block being located against movement axially of the screw between the ball race and a shoulder 28 formed by the reduced diameter portion 25. As will be evident, rotation of the screw will produce movement of the pivot blocks 18, 19 towards or away from one another and consequent variation in the spacing of the upper and lower pivot rods 14, 15.

The upper pivot rod 14 also has fulcrumed thereon a load-engaging member 30 which extends between the two toggle link systems, while the lower pivot rod carries a ground-engaging member 31 which is freely rockalble so as to rest evenly on the ground irrespective of the camber or slope. The load-engaging member is constructed for co-operation with a part of the vehicle chassis in such manner that the device is suspensible from the chassis. To this end, the member 30 is of inverted U-shaped cross-section and has welded to its upper face a pair of laterally spaced inturned L-shaped ribs 32 which are adapted to be slid over a rail 33 of dat metal bar carried by a bracket 34 xed to the vehicle chassis. The height of the channel provided by the ribs 32 is greater than the thickness of the rail so that in the freely suspended position of the device there will be a clearance between the bottom of the rail and the top of the loadengaging member. This enables a pair of dowels formed by the heads of bolts 35 by which the rail is secured to the bracket 34 to be aligned with openings 36 provided in the top wall of the member 3G and to enter said openings when the device is extended to contact the ground and raise the vehicle, thus preventing relative movement of the load-engaging member and rail in the lifting position of the device. The space between the ribs 32 is bridged at one end to provide an abutment 37 which limits inward movement of the member 3l) along the rail by engaging the outer end of the bracket 34 and aligns the openings 36 with the bolt 35. The rail 33 may be horizontal or, as shown, may be upwardly inclined towards its free end at about 5 to the horizontal, being preferably mounted so as to extend laterally from the chassis with said end about ush with the edge of the running board or the side of the vehicle body.

The provision of a pivoted load-engaging member 30 and a pivoted ground-engaging member 31 ensure that a rm bearing shall be effected both on the ground and on the vehicle irrespective of the camber or other inclination of the ground and of the angle of tilt of the vehicle during lifting. It is important, however, that during the operation of extending the jack to make contact with the ground the load axis, i. e., the plane through the upper and lower pivot rods 14, 15, shall be as near vertical as possible. This requires that the actuating screw 23 shall be horizontal or substantially so, but as this generally necessitates stooping on the part of the operator, there may often be a tendency to lift the outer end of the screw. To prevent such a contingency the jack, in accordance with a further feature of the invention, is provided with means which, once it has been fitted on the rail as above described, ensures that the load axis is correctly positioned and will not deviate therefrom during the lifting operation more than is required by the tilting of the vehicle. One such means will now be described with reference to Figures l and 2.

Journalled in the side arms of the load-engaging member is a bar 40 to which is attached one end of a resilient link generally designated by the numeral 41, the other end of said link being pivotally connected at 42 to a bracket 43 Welded to the pivot block 18, said link tending to urge the load-engaging member 30 about the pivot rod 14 to a mean position. The bar 40 and bracket 43 are so located that the link 41 lies parallel to the adjacent link 10 of each toggle system within the compass of the two systems so as not to increase the overall size of the jack in its collapsed condition. As illustrated, the resilient or parallel link comprises two members arranged one within the other and capable of relative longitudinal movement, one of said members being in the form of a rod 44 having an end portion 45 of reduced diameter passing through a transverse aperture in the bar 40 and xed thereto by a nut 46, while the other member consists of a tube 47 surrounding the greater part of the rod 44 and welded at one end to an arm 48 pivoted on the bracket 43. At its opposite end the rod 44 carries a washer 49 which is slidable thereon and is maintained on said rod by a nut 50. The arm 48 has a recess 48a which receives the nut 50. A compression spring 51 coiled about the rod 44 has one end bearing against the Washer 49, its other end engaging a second washer 52 which is also slidable on the rod. The washer 49 is pressed by the spring 51 against the end of the arm 48 and the washer 52 is similarly pressed by the spring against the flanged end 53 of a sleeve 54, said sleeve being secured against withdrawal from the tube by a plug 55 threaded into said tube and serving to maintain the rod and tube in axial alignment.

In Figure l the position of the parts corresponds to the normal or non-lifting condition, the length of the link 41 and consequently the inclination of the load-engaging member being such that when said member is located in position on the rail 33, the load axis through the pivot rods 14, 15 will be substantially vertical assuming the vehicle to be on a more or less flat or at the most slightly cambered surface. Similarly the screw axis will then be substantially horizontal and the device will be maintained with said axes in substantially the same planes while the jack is being extended to engage the ground, when the foot 31 will pivot to rest accurately thereon. When, thereafter, the screw is further actuated to lift the vehicle, the inclination of the vehicle chassis will be communicated through the rail to the load-engaging member and the link 41 will become extended or contracted, either action being effected against the force of the spring. If, for example, the load-engaging member 30 tilts in relation to the rest of the jack so that the link 41 is extended, the rod 44 and tube 47 moving relatively outwardly, the rod 44 and washer 49 are drawn upwardly away from the arm 48, thus further compressing the spring and so increasing the resistance provided against change in the direction of the load axis or the screw axis. if the loadengaging member should be tilted in relation to the rest of the jack in the opposite direction so that the link 41 is contracted, the rod 44, washer 52 and sleeve 54 will be forced downwardly by the bar 4t? which, as shown, normally abuts the outer end of said sleeve. The spring is thus further compressed to produce the same effect as in the previous case.

Figures 3 and 4 show another embodiment of jack according to ,the invention in which the mean angular position of the load-engaging member is determined by a spring which normally couples said member to the two upper links 10, 11 of each toggle system. As illustrated, a pre-stressed semi-elliptic leaf spring 60 is interposed between the flat top portion of the load-engaging member 30 and a pair of rods 61, 62 which are carried transversely between the corresponding links 10, and 11, 11 of the two toggle systems. The spring 60 is located relatively to the load-engaging member by a rivet 63 which passes freely through an opening 64 in the spring, the head 65 of said rivet serving as a dowel which is adapted to engage an opening provided in the suspension rail 33 so as to hold the jack against movement relatively to the rail when in its lifting position. Also engaged with the under side of the spring is a pair of rods 66, 67 carried between the side arms of the load-engaging member at either side of the pivotal axis 14 of said member, the purpose of which is to prevent equalization of the spring pressure on the rods 61, 62 when the load-engaging member is tilted from its mean position by relieving one rod from the force of the spring as the load on the other is increased. As will be seen, the pin 61 is somewhat higher than the pin 62, whereby the load-engaging member in its mean position is inclined so that, when engaged with a similarly inclined rail as in Figures 1 and 2, the load axis -of the jack will be substantially Vertical.

ln Figures 3 and 4 the jack is shown sufliciently extended to bring the rods 61, 62 away from the spring, but the spring will press on the pins in the collapsed `condition of the jack and during its extension into contact with the ground.

While particular embodiments of the invention have been described, it is to be understood that these are by way of example only and that modications may be introduced within the scope of the appended claims.

We claim:

l. A lifting device having upper links, the upper ends of which are connected pivotally on a rst common axis on which a load engaging member is pivotally mounted, and having lower links the lower ends of which are connected pivotally on a second common axis on which there is a ground engaging member also pivotally mounted, operating means for moving the other ends of said upper and lower links to and from each other, resilient means comprising a link coupled to said load engaging member at a point offset from the pivotal axis of said member, a pivot block carried by said device and positioned adjacent said operating means and one of the other ends of one of said links, said resilient means having one end coupled to said pivot block and extending substantially parallel to that one of said links interconnecting said load engaging member and said block in at least one of its positions with respect to said load engaging member, said link being resiliently deformable along its axis under both compression and tension forces.

2. Device as claimed in claim 1, wherein the resilient link comprises a rod and a tube respectively pivotally connected to the load-engaging member and the said pivot block and arranged one within the other for relative axial movement in either direction, a coiled compression spring within said tube and surrounding the rod, means limiting extension of the spring in either direction, and a sleeve interposed between an abutment on the load-engaging member and the adjacent end of the spring, whereby the spring will be further compressed upon relative movement of the rod and tube in either axial direction.

3. A lifting device comprising an upper set of links and a lower set of links, said sets of links being pivoted together at their outer ends, pivot blocks mounted between the upper and lower sets of links at the points at which said sets of links are pivoted together, a load engaging member pivotally connected to said upper set of links, a ground engaging member connected to said lower set of links, a link connected between one pivot block and the load engaging member, said link being connected to said load engaging member at a point offset from the pivotal connection between said load engaging member and said upper set of links, said link being substantially non-deformable in directions transverse to the length thereof and offering a resilient restraint against deformation along its longitudinal axis.

4. A lifting device of the lazy-tongs type comprising a pair of pivotally connected upper links and a pair of pivotally connected lower links articulated to said upper links, operating means for moving the articulated ends of the links towards and away from each other, a load engaging member tiltably mounted in relation to said links on the pivotal axis of the upper pair of links, a ground engaging member freely tiltable in relation to said links on the pivotal axis of the lower pair of links, and means for resiliently restraining the load engaging member against tilting movement over at least part of the opening movement of the jack, pivot blocks connecting the articulated ends of the link acted upon by said operating means, said means for resiliently restraining the load-engaging member comprising a link substantially non-deformable in directions transverse to the length thereof and offering resilient restraint against deformations thereof along its longitudinal axis.

5. The combination set forth in claim 4, said link forming part of said means for resiliently restraining the loadengaging member comprising a rod and a tube respectively pivotally connected eccentrically to the load-engaging member and one of said pivot blocks and arranged one within the other for relative axial movement in either direction, a coiled compression spring within said tube and surrounding the rod, means limiting extension of the spring in either direction, an abutment on the load engaging member, a sleeve interposed between said abutment on the load engaging member and the adjacent end of the spring, whereby the spring will be compressed upon relative movement of the rod and tube in either axial direction.

References Cited in the file of this patent UNITED STATES PATENTS 1,576,721 Conrad Mar. 16, 1926 1,664,579 Twyman Apr. 3, 1928 1,810,657 Kohler June 16, 1931 1,994,015 Curran Mar. 12, 1935 2,112,169 Leitch Mar. 22, 1938 

